1. Field of the Invention
This invention relates generally to spinal implants and, in particular, to a spinal implant having a novel top-loading bolt attachment for support and alignment rods with cross links and ancillary components for stabilization of the vertebrae as well as a two plate system for cervical spine fixation.
2. Background of the Invention
Surgical implants are well known in the art for treatment of curvatures of the spine including anterior, trauma, deformity, and/or degenerative spinal conditions. The purpose of the implant is to reinforce the spine by use of strategically placed attachment screws capable of supporting alignment support rods placed bilateral along the vertebrae as well as cross-link members that bridge the sagittal of the spine.
The problem which this invention addresses is the method of fastening the spinal implants during surgery. Conventionally, the placement of an attachment screw provides the functional base for the support rod, cross-link, caudal facing hooks, cranial facing hook and the like components that form a spinal implant system. The conventional method of fastening utilizing a goal post mounting screw from which a bolt and nut is coupled perpendicular thereto for mounting to the component. This side attachment frequently requires the movement of muscle and other tissue during operation which increases the difficulty of the operation, is a time consuming effort, and can be a major trauma to a person.
In addition, the use of the prior art devices required pre-thought to where the cross-links are to be placed. Once the base screws are installed, they cannot be moved and if the screws are placed incorrectly, the cross-link will not fit.
U.S. Pat. No. 5,084,048, issued to Jacob et al., entitled "Implant for Vertebrae With Spinal Stabilizer" discloses a vertebrae implant having a stabilizing element which is articulated to accommodate a pair of bone screws wherein each bone screw includes a clamp disposed between a shoulder in a spherical surface which is all coupled together by the use of a clamping nut directly on the end of the bone screw. The device allows for support of an alignment rod along the side of the bone screw, but fails to provide any type of cross link or ancillary component attachment devices.
U.S. Pat. No. 4,041,939, issued to Hall, entitled "Surgical Implant Spinal Screw" discloses a spinal implant utilizing a screw having a centrally disposed aperture for placement of a metal cable therethrough with a nylon insert that will permanently secure the cable in a fixed position once attached. The device is best used in an operation for the correction of scoliosis.
Another problem with prior art is the use of anterior cervical plates. The prior art employs a single plate that is attached by the use of small bone attachment screws. After installation, the screws have a tendency of working their way out of the bone resulting in the loosening of the cervical plate causing the patient pain and typically resulting in further surgery to correct the problem.
Therefore there exists a need to correct the aforementioned problems by use of a top loading spinal implant system and associated cervical plate attachment cover.